The invention of the transistor in 1948 was quite probably the most important technological development of the 20th century, if not all time. The transistor made it possible to construct computers of reasonable size and cost, and of much greater speed and data handling capability, and reduced power consumption than vacuum tube computers which it replaced. In the latter part of the 1950s, transistors were introduced to a wide variety of military, industrial and consumer products.
In the early 1960s, integrated circuits were introduced. Integrated circuits contain a number of transistors and interconnecting circuit elements which together comprise an operable electronic circuit, such as a logic element, amplifier, or memory element. While the first integrated circuits contained just a few transistors, integrated circuits are now being manufactured which contain tens of thousands of transistors on a single semiconductor die or chip.
Integrated circuits are fabricated from thin slices of a semiconducting material such as silicon, germanium, or gallium arsenide. The slices are cut into small squares or rectangles referred to as chips or dice, ranging in size from squares about 100 mils. on a side to several hundred mils. on a side. Transistors, diodes, resistors and interconnecting circuit paths are formed on the chip or die by diffusing impurities into selected regions of the chip, and by depositing various conducting paths and insulating layers onto the chip.
After a semiconductor chip or die has been fabricated as described above, it must be attached to a base or carrier forming part of a package or container to protect the delicate die from damage. Included in the packaging operation is the interconnection of conductive pads providing input and output ports to the die, to more robust leads or terminals which extend outward through a container or package used to enclose the die.
Most integrated circuit or discrete semiconductor device chips tend to be rather fragile because of their small size and thickness. The small size and fragility of semiconductor dice necessitates that special care be exercised in the manipulation of the dice during the manufacturing steps required to make finished devices. One method of handling semiconductor chips that has proven to be highly successful employs a vacuum probe or tube. Apparatus employing the vacuum probe method moves a flat open end of a tube into contact with the flat surface of a die, produces negative pressure in the tube to hold the die by suction while the tube and die are transported to a desired location and then releases the vacuum pressure to deposit the die at a desired location. A method and apparatus employing the above principles is disclosed in U.S. Pat. No. 3,855,034, Dec. 17, 1976, Miller, Method and Apparatus For Bonding In Miniaturized Electrical Circuits, issued to one of the present inventors. The use of a vacuum probe to manipulate semiconductors has proven to be a highly satisfactory method for manipulating a wide variety of semiconductor dice, of the type bearing one or more transistors, and integrated circuits having many transistors and associated circuit elements. However, there are some types of semiconductor chips or dice which may not be picked up with a vacuum probe, for reasons which will now be described.
Certain semiconductor chips, such as those made of gallium arsenide and used to make microwave field effect transistors (FETS) are so thin and fragile that a force of as small as a few grams applied to their planar surfaces will readily break the chips.
The present invention was devised to provide a method and apparatus for manipulating extremely fragile semiconductor dice, and for attaching dice of that type to a base or carrier.